Car's Speedo wont work and tranny malf

run the fault but all you describe is operated from the VSS sensor ( vehicle speed sensor)
it tells the cruise control the vehicle speed , tells the TCM the vehicle speed so that ratios can be changed, activates the speedo,and will report with a check engine light to report a transmission problem
run the fault codes first

a real DTC code.
17 , 94 Accord
the means VSS is dead, vehical speed sensor (miles per hour)
so , that begs the question is the speedometer dead or odometer
dead or acting funny IN ANY WAY?
is this an A/T Car or M/T car, both have VSS, so... cant answer.
Auto or stick, ill pretend, AUTO.
VSS moves all over the place, in all cars. all models and all years.
on this car, its odd.
quote FSM:
Accords and Preludes use an external sensor mounted on top of the power steering speed sensor in the engine compartment. The power steering speed sensor is gear-driven and controls the steering boost in relation to the speed of the vehicle. An electric pulser unit is mounted on top of this unit and is coupled to it by a small shaft. The motion from the lower unit is transferred to the upper unit; the resultant electrical signal is sent to the appropriate control units.

most cars old use the speedometer VSS sensor inside
on newer cars 1996 (on avg) the sensor is on the tail shaft. and in speedo.
on very new cars there are 3 VSS.... (dont ask)

on my 96 car, the tranny VSS can fail and then FALL back to the
SPEEDO head. and tranny still shifts but is funky,
the FSM covers all this, i recommend getting one, to understand
how it all works.

your car has and electronic speedometer
the VSS orange wire , sends speed data to the PCM, TCM, cruise.
the PCM then sets the speedo dial, and uses this info to run TCM
controls to the transmission.
your orange wire signal is dead or flaky.

Im having trouble as well with shifting higher than second gear and me speedo doesn't work.checked all fuses replaced vss (both) and still no speedo or shifting. any ides would be great. I have power at buffer and tranny

97 c1500 or k1500,. not told. just 1/2 ton sure. K1500 is 4wd got that?
the 4wd sensors are not the same. ok? no engine told either, guess 4.3L only
4L60-E; 4 speed Automatic trans. or 4L80e
that is and E box, electronically TCM shifted.
and the speed sensors must all work!! must !
it it can not shift correctly.
that is a fact.
you replaced 1 but never say the speedo was fixed, yes the speedo matters
OD is 4th gear,
the TCM can be scanned, why not do that?
stuck in 2nd gear is common for TRANNY LIMPHOME
it does that when sensors or solenoids go bad.
making car safe to drive to a shop only that is all limphome means just that.
beats a 100% dead car no? for sure.

sensors all 2, input speed and outputs speed, and if 4wd OSS is on the rear of 4wd transfer care, moved, for 4wd.
solenoids not bad in box. 1>2 and 2>3 shift and 3<4 shift.
scan the TCM.

the ECM on the car 4.3L runs the Tranny (TCM logic) 12 connection.
so not scanning the ECM OBD2 port ,you fully miss the boat and it sailed
the good ship of facts gone. DTC errors for sure missed.

have a tranny filter fuid change soon

the trans computer has seen a problem possible a bad sensor, or an internal problem, and puts it into a safe mode, or limp home mode , it wont shift , it will stay in 3rd gear, this way this reduces the possibility of further damage trans damage, when you turn the ignition off and back on it resets the tcm, my advice is to take it to your local dealer, they can diag your trans as they know the product, i dont advise pep boys, or discount auto parts.

check your idle control valve/sensor and torque converter/solenoid these four things are common problems

good diagnosis that is correct if the vehicle speed sensor is not working the speedo doesnt work and the trans doesnt know when to shift

Possibl eclogged cat converter,will cause miss and sluggish trans responce.

could be one of three things 1) could be a bad sensor 2) could be a wiring concern 3) could be a computer concern